1. Field of the Invention
This application relates to improvements in dual temperature exchange systems for concentrating a desired material by exchanging, at different temperatures, said desired material with another material between chemically different lighter and heavier fluids which are physically separable from each other and which are each capable of containing each of said materials.
2. Description of the Prior Art
In such dual temperature exchange systems, for instance, as disclosed in my prior U.S. Pat. Nos. 2,787,526 issued Apr. 2, 1957; 2,895,803 issued July 21, 1959; and 3,142,540 issued July 28, 1964 and my heretofore filed copending U.S. Patent Applications including, inter alia, Ser. No. 828,926, filed July 16, 1959 (abandoned and replaced by a continuation and two divisions, namely: Ser. No. 123,815, filed Mar. 11, 1971 (now U.S. Pat. No. 3,933,995 issued Jan. 20, 1976), Ser. No. 712,287, filed Mar. 11, 1968, now U.S. Pat. No. 3,907,509, issued Sept. 23, 1975, and Ser. No. 797,191, filed Feb. 26, 1969, now U.S. Pat. No. 3,907,508, issued Sept. 23, 1975); Ser. No. 587,362 filed Sept. 26, 1970 (now U.S. Pat. No. 3,907,500, issued Sept. 23, 1975, Ser. No. 587,363, filed Sept. 26, 1970 (now U.S. Pat. No. 3,920,395, issued Nov. 18, 1975); and Ser. No. 597,365, filed Sept. 28, 1966 (abandoned and replaced by a continuation and two divisions, namely: Ser. No. 214,494, filed Dec. 30, 1971, Ser. No. 201,238, filed Mar. 22, 1971 and Ser. No. 43,626, filed Apr. 30, 1970 (abandoned and replaced by Ser. No. 330,327, filed Feb. 7, 1973, (now U.S. Pat. No. 3,821,833, issued Mar. 18, 1975)) (the disclosures of all said patents and applications being incorporated herein by reference), a system is employed which comprises one or more stages of hot and cold tower pairs for contacting of said lighter and heavier fluids in countercurrent relationship. In such known systems one of the two fluids is supplied from an external source and is fed to the first tower of the first stage pair of towers, enriched in the desired material to be concentrated by preferential exchange therein, impoverished in the said desired material in the second tower of said pair to a concentration of the desired material less than that of said feed supply fluid, and discharged from the system. The other fluid is continuously circulated through the pair of towers to become enriched in the desired material in the second tower of said pair and to become impoverished in that material in the first tower of said pair. Such a system may comprise a plurality of similar or different concentrating stages of known species, and a portion of the flow of one or both of the enriched fluids being passed between said towers in a stage other than the last is also impoverished in the desired material during such passage by subjecting it to extraction of desired material therefrom in the following stage or other concentrating treatment. A portion of the enriched flow of one of the fluids is withdrawn as product from that part of the system in which its concentration of the desired material is high.
Also, in such dual temperature exchange systems, as is shown by the above mentioned prior patents, various provisions are made for moving the process fluids and adjusting the temperatures thereof as required by the process, which employ fluid pumping means, heating and cooling means, and indirect and/or direct contact heat exchange means provided to meet the particular requirements of the system.